South Africa (SA), a resource limited setting with the world?s largest population of people living with HIV, has hundreds of thousands of youth living with perinatally acquired HIV (PHIV) who are rapidly becoming adolescents and young adults. Adolescents with PHIV must contend with the negative effects of life-long viral infection and chronic inflammation on their neurodevelopment, medical status, mental health, and, for many, the demands of lifelong ART adherence ? placing them at risk for not achieving these important milestones. Neurocognitive impairment (NCI) is chief among these negative effects. NCI in adolescents with PHIV most commonly affects the neurocognitive domains of working memory, executive function and processing speed, and may be particularly vulnerable to NCI related to the prefrontal cortex, which plays a key role in cognitive flexibility, response inhibition and attentional control (i.e., executive functioning). NCI can affect youth?s ability to perform in and complete school, interact successfully with peers and adults, find employment, initiate and maintain long- term relationships, and function independently. NCI can also interfere with adherence to medication, which is critical in HIV, and increase poor decision-making and greater HIV transmission risk behaviors (e.g., unprotected sex). The first step in addressing NCI adolescents with PHIV is detecting and diagnosing it, but doing so in South Africa is seriously hampered. Few neurocognitive tests exist for the hundreds of thousands of youth with PHIV in SA. The tests that do exist require highly trained personnel to administer and score, take several hours to administer, lack ecological validity to predict real-world outcomes, and many suffer from cultural biases because they were developed for and normed on youth in the US or Europe. Given how overburdened the SA healthcare system is and its reliance on task-shifting various components of care to lay health workers (LHWs), without accurate, clinically useful, and relatively brief neurocognitive tests that can detect NCI and meet the demands of task-shifting in resource-limited settings, adolescents with PHIV in SA will not be assessed, missing opportunities to detect NCI and intervene. This supplement will develop and add two new tests of executive functioning to the NeuroScreen app that is being evaluated in the parent study (R01 HD095256; PI: Robbins), and will strengthen our ability to detect executive functioning problems in youth with PHIV in SA ? key neurocognitive domains that may be particularly vulnerable in adolescents with PHIV and are highly related to academic, behavioral and health outcomes.